Marx and colleagues have shown that the use of platelet concentrate represents an innovative method to modulate and accelerate wound healing process, as well as bone regenerative processes (Oral surg., Oral Med., Oral Path 1998, 85: 638-646). Therefore these authors elaborated a technique allowing to isolate and precipitate platelets thereby obtaining an autologous platelet concentrate, which is neither toxic nor immunoreactive. This substance is able to enhance the effects of growth factors contained in platelets granules and which are initiators of metabolic pathway involved in wound healing steps.
According to Marx's protocol encompassing the use of a cellular separator, the platelet concentrate is prepared by carrying out a venous blood sample of 500 ml, namely an operation which is accomplished by means a venous catheter. The platelet concentrate is subsequently activated with calcium chloride and bovine thrombin to produce a platelet gel which can be combined with either autologous spongy and cortical bone or bone matrix consisting of bio-glasses.
In Italy Marx technique for the activation of a platelet gel cannot be carried out since bovine thrombin is no longer available on the market. In addition this method involving the use of very high amounts of blood requiring specific instrumentation and skilled personnel for preparing platelet concentrate, cannot be realised in a medical surgery so as to allow a routine use of the platelet gel.
In U.S. Pat. No. 5,585,007 and WO 98/11925 methods for preparing platelet gel are disclosed. These methods, although representing an improvement if compared to Marx's protocol, as they necessitate much lower blood amounts (50-60 ml), they require for platelet gel formation the use of bovine or human thrombin.
To date human thrombin can only be prepared by DNA recombinant technique. In Italy substances prepared according to this technique can be used only for in vitro experiments, but not for in vivo experiments.
Technical Problem
The need was felt of a process for preparing a platelet gel not presenting the prior art processes drawbacks, connected with the use as the activator of human or bovine thrombin.